Only AQ salt can be used for fin-rot, though. Well, something this advanced anyways. His fins are almost completely gone and his ventrils are starting to curl. Even with the 3 50% water changes a day it's barely slowing down!

I would break down and get a fin rot med. If its not slowing with the salt treatments then I would stop those. Ventrals curling is from hard water (nothing to worry about there) but the fins almost gone is a big deal. You have to stop it before it reaches his body. Once it reaches there its very hard to get him back from that.

The maximum amount you can safely go up to is 3 tsps for aquarium salt. Can you post a pic of his fins? If it's really severe, you may need to switch to a med such as API Furan-2 or even better, Seachem Kanaplex.

Last night I tried the stress coat. This morning he had a bubble nest, which makes me a bit less worried....that didn't stop me from stopping at Petco on the way home. They didn't have any of that Seachem but I DID get the other one. I'm going to try it tonight as a last resort.

Also, I need some water chemistry help. I have been trying to recycle my old platy tank...

The Ammonia is zero, but the nitrites and nitrates were so high that my chart couldn't tell me HOW high. I did a 75% water change, and now they are low enough on my chart but still almost to where it's too high again.

Yeah, Zacky, the Seachem one is very hard to find. 9/10 it has to be ordered online so don't worry that you didn't find it.

As for your tank . . . YIKES! Those are some crazy nitrates. Do another water change to get the levels down. Have you been changing the water at all since you started trying to recycle it? It's possible the levels just built up. Basically, just keep doing water changes until the nitrates come down. It sounds like, since your nitrate levels are sky high and your ammonia is 0, that your tank is pretty much cycled. Just keep a very close eye on it for the first few weeks and do water changes any time the levels get crazy.